FIG. 1 depicts a schematic diagram of telecommunications system 100 in the prior art. Telecommunications system 100 comprises affiliated off-premises telecommunications terminals 101-1 through 101-N, wherein N is a positive integer; unaffiliated off-premises telecommunications terminal 102; affiliated on-premises telecommunications terminals 103-1 through 103-N; private branch exchange telephone system 104; and telecommunications network 105, interconnected as shown.
The terms “affiliated” and “unaffiliated,” as they apply to the off-premises terminals, refer to whether an off-premises terminal is affiliated with an on-premises terminal (i.e., a terminal served by private branch exchange 104). The relationship of an on-premises terminal (e.g., terminal 103-1, etc.) with an affiliated off-premises terminal (e.g., terminal 101-1, etc.) is described below and with respect to FIG. 2, with regards to extending a received call to one or both terminals.
Private branch exchange 104 is capable of switching incoming calls from telecommunications network 105 (e.g., the Public Switched Telephone Network, etc.) via one or more transmission lines to any of on-premises terminals 103-1 through 103-N. Private branch exchange 104 is also capable of handling outgoing calls from any of on-premises terminals 103-1 through 103-N to telecommunications network 105 via one or more transmission lines that connect private branch exchange 104 to telecommunications network 105.
Private branch exchange 104 is capable of also extending an incoming call to a telephone number in telecommunications network 105, in addition to switching the incoming call to on-premises terminal 103-n, wherein n has a value between 1 and N, inclusive. The telephone number that is extended-to in telecommunications network 105 corresponds to an affiliated terminal 101-n.
In addition, private branch exchange 104 is capable of providing telecommunications features that enable the forwarding of calls, the transferring of calls, conferencing, etc.
FIG. 1 also depicts the address spaces that are relevant to telecommunications network 100 in the prior art. The term “address space” refers to an addressable region of telephone service. Address space 111 represents the addressable region served by telecommunications network 105. Address space 112 represents the addressable region served by private branch exchange 104.
Private branch exchange 104 exists in both address space 111 and address space 112, and acts as a “bridge” between the two address spaces. When a calling party places a call to someone served by private branch exchange 104, the calling party uses a dialing sequence that includes a telephone number that belongs to telecommunications network 105 and residing in address space 111. As part of the dialing sequence, the calling party also uses an extension number that allows access to one of the on-premises telecommunications terminals that reside within address space 112.
Thus an on-premises telephone number is one that exists within the address space of the private branch exchange, and an off-premises telephone number is one that exists within the address space of the Public Switched Telephone Network.
FIG. 2 depicts a flowchart of the tasks that are relevant to processing an incoming call in the prior art. To accomplish tasks 201 through 203, private branch exchange 104 maintains a table that correlates telecommunications network number to private branch exchange extension. Table 1 depicts an illustrative table that correlates telecommunications network number to private branch exchange extension.
TABLE 1Extension-to-Number DatabasePrivate BranchTelecommunicationsExchange ExtensionNetwork Number732-555-0102, x11201-555-1236732-555-0102, x12908-555-3381. . .. . .732-555-0102, x99212-555-6784
At task 201, private branch exchange 104 receives a call from telecommunications network 105, where the call is originated by unaffiliated telecommunications terminal 102.
At task 202, private branch exchange 104 extends the call to a first telephone number. The first telephone number exists in the address space of the private branch exchange, namely address space 112, and can be associated with one of on-premises terminals 103-1 through 103-N. The first telephone number is represented as the private branch exchange extension in Table 1.
At task 203, private branch exchange 104 also extends the call to a second telephone number. The second telephone number exists in the address space of telecommunications network 105, namely address space 111, and can be associated with an affiliated, off-premises terminal such as affiliated telecommunications terminal 101-n.
Referring to the example in Table 1, the call, placed to 732-555-0102, extension 11 (i.e., shown in the first row), is connected to private branch exchange extension 11 and is also forwarded to telecommunications network number 201-555-1236.